Primary recrystallized textured iron alloy member having an open gamma loop

ABSTRACT

An iron base alloy is described which contains low amounts of alloying elements and is suitable for use as a transformer core material. The alloy is characterized by a (110) texture, and a primary recrystallized and normal grain growth microstructure. The process for obtaining the oriented structure is either a two stage or a three stage process in which the final cold reduction effects only a moderate reduction in cross-sectional area to finish gauge. In all cases the alloy is subjected to a final anneal at a temperature below the Ac1 temperature of the alloy.

Bite States atent 1 Thornburg 11] 3 Nov. 119, 1974 PRIMARYRECRYSTALLIZED TEXTURED IRON ALLOY MEMBER HAVING AN OPEN GAMMA LOOP [75]Inventor: Donald R. Thornburg, Pittsburgh,

[73] Assignee: Westinghouse Electric Corporation,

Pittsburgh, Pa.

[22] Filed: Dec. 11, 1972 [21] App]. No.: 312,681

Related U.S. Application Data [63] Continuation-impart of Ser. No.228,318, Feb. 22,

1972, abandoned.

[52] U.S. Cl. 148/31.55, 75/123 R, 75/123 L, 148/112, 148/120, 148/121[51] Int. Cl C04b 35/00 [58] Field of Search 148/120, 31.55, 121, 111,148/112, 113; 75/123 R, 123 L [56] References Cited UNITED STATESPATENTS 3,130,094 4/1964 Kohler et al. 148/111 3,180,767 4/1965 Eastonet al. 148/120 11/1966 Koh ..148/113 10/1967 Carpenter et al 148/111OTHER PUBLICATIONS Pyr, R., Development Met. Structure and Mag. Prop. inFei Alloys, in J. Appl. Phys. Suppl. to Vol. 30 (1959) 1895-1935.

Lyman et al., Metals Handbook, Cleveland (ASM) 1961, pp. 62 & 785487.

Primary ExaminerWalter R. Satterfield Attorney, Agent, or Firm-R. T.Randig [5 7] ABSTRACT An iron base alloy is described which contains lowamounts of alloying elements and is suitable for use as a transformercore material. The alloy is characterized lg! a (110) tte ture, and aprimary recrystallized 4 Claims, 12 Drawing Figures Pmammfivw 3.8492 1 21 sum 10F e ROLLING DIRECTION DlGIT CONTOUR 50 I 1'.0 2 2.0

o 3 3.0 4 4.0 0 5 5.0 1 E3 3 2-2 f 1 I I I I l l l I f I. I I I I I l 9075 60' 45 30 l5 0 ALPHA FIG; IA

VPATENTELHUVIQIQN 3.849.212

SHEEI 2 BF 6 ROLLING DIRECTION 40 Z DIGIT CONTOUR 9 3O 1 |.0 5 2 2.0 g20 3 30 u- 4 4.0 IO 5 W l Ii I I 1 l l l l PATENTEL n 1 I 3. 4-9.2 ;12

sum star 6 ROLLING DIRECTION FIG. 3

men CONTOUR 4O 1 1.0 2

OI F l l l l l I I l I l' l I I I I 7 ALPHA FIG. 3A

PATENTi-LL v 3. 849 ,2 1 2 saw u or e ROLLING DIRECTION 4 0 men CONTOUR49 l 1.0 Z 2 L5 930 3 2.0 5 4 3.0 5 4.0 E 6 4.9

OIIIIIIIIIIIII'F 75 so 45' 30 l5 0 PATENTELHUYI 91914 3,849,212

SHEET 50F 6 ROLLING DIRECTION so DKISIT couzTguR 2 3:0

o 75 so .45 30 I5 0 ALPHA FIG; 5A

PATENTL, ::av 1 9 I974 SHEET 8 OF 6 ROLLING DIRECTION DIGIT CONTOURALPHA 3 2 zorroqmm FIG. 6Av

PRIMARY RECRYSTALLIZED TEXTURED IRON ALLOY MEMBER HAVING AN OPEN GAMMALOOP CROSS REFERENCE TO RELATED APPLICATIONS Status Serial No. FilingDate Copending 228,071 Feb. 22. I972 Copending 228,319 Feb. 22. I972 nowabandoned 228.070 Feb. 22, 1972 now abandoned 228,320 Feb. 22. I972 IBACKGROUND OF THE INVENTION 1. Field of the Invention The presentinvention relates to an iron base alloy which contains low amounts ofalloying components and which, when processed in accordance with eitherone of the two methods set forth hereinafter, will produce an orientedgrain structure in the finished product which is characterized by acube-on-edge orientation or as described in Miller lndices as (I10)[001] grain orientation, and comprising a primary recrystallized andnormal grain growth microstructure. Such magnetic materials are useful,for example, as core materials in power and distribution transformers.

2. Description of the Prior Art The operating inductions of a largeproportion of todays transformers are limited by the saturation value ofthe magnetic sheet material which forms the core. In extensive use todayis an iron base alloy containing nominally 3.25% silicon which isprocessed in order to obtain a cube-on-edge or l l)[00l] grainorientation in the final product. An example of this well known steeldepending upon the final magnetic characteristics is called type M- andhas the final grain orientation developed by means of a secondaryrecrystallized microstructure. This microstructure is attained duringfinal box annealing in which preferentially oriented grains grow at theexpense of non-preferentially oriented grains with the result that thealloy usually has an extremely large grain size such that the diameterusually greatly exceeds the thickness of the sheet material. However, inorder to obtain such large grains in a secondarily recrystallizedmicrostructure it requires a long time, high temperature heat treatmentfor the development of the orientation. This anneal is also required forthe removal of residual sulfur content. Sulfur contents in excess ofabout 100 ppm in the finished product adversely affects the magneticcharacteristics exhibited by the silicon-iron alloy.

In addition to the long time, high temperature box anneal, which isquite costly, the addition of 3.25% silicon to pure iron, whileeffective and generally desirable for greatly improving the volumeresistivity, nonetheless lowers the saturation value so that in mostcommercially produced iron-3.25% silicon containing alloys, thesaturation value of such alloys usually does not exceed 20,300 gauss.Thus, there is the obvious tradeoff of improved volume resistivity whichrelates to the core losses of the material for lower saturation value,since the saturation value of commercially pure iron is about 21,500gauss. It will be recognized further that such saturation values areonly obtained where the material possesses a high degree of l l0)[00l 1orientation in the final product. Moreover, since commercial iron willhave substantially higher watt losses and substantially higher coerciveforce values than silicon steel it was prudent to balance the overallobserved magnetic characteristics and the best balance heretoforeobtained was that of the iron 3.25% silicon alloy which exhibited thecube-on-edge orientation.

The alloy of the present invention also employs a trade-off of thevarious magnetic characteristics. The observed magnetic characteristicsespecially those where the material is used as in transformer coreapproach those of the commercially produced 3.25 silicon steel materialsemployed today. The present low alloy composition is radically alteredfrom the 3.25% silicon containing iron, but the same orientation isattained by means of the processes set forth hereinafter so that themicrostructure is primarily recrystallized with normal grain growth.Thus the alloy of the present invention produced comparable magneticcharacteristics without employing the costly secondarily recrystallizedmicrostructure, yet obtains the same orientation in a composition whichis quite diverse from that of the commercially used materials.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a (1 l0) Pole Figure andFIG. 1A is a Histogram for Heat No. 1482;

FIG. 2 is a (200) Pole Figure and FIG. 2A is a Histogram for the samematerial of FIG. 1;

FIG. 3 is a (1 l0) Pole Figure and FIG. 3A is a Histogram for acommercial size heat identified as Heat No. 3524;

FIG. 4 is a (200) Pole Figure and FIG. 4A is a Histogram for thematerial of FIG. 3;

FIG. 5 is a I I0) Pole Figure andFIG. 5A is a Histogram for anothercommercial size heat identified as Heat No. 3523; and

FIG. 6 is a (200) Pole Figure and FIG. 6A is a Histogram of the materialof FIG. 5.

SUMMARY OF THE INVENTION The present invention relates to an iron basealloy containing up to about 0.03% carbon, up to 1% manganese, fromabout 0.3% to about 4% of at least one of the volume resistivityimproving elements selected from the group consisting of up to about 2%silicon, up to 2% chromium, and up to about 3% cobalt, and the balanceessentially iron with incidental impurities. This alloy is processed byhot working and cold working in either a two or a three stage operation,the final stage of working effecting only a moderate reduction in thecross-sectional area of the material being processed, said lastreduction in cross-sectional area lying generally within the rangebetween about 50% and about The finish gauge material is thereaftersubjected to a final anneal at a temperature which is in the rangebetween about 750C and the Ac, temperature exhibited by the alloy. Asthus produced, the alloy exhibits a cube-on-edge or a I l0)[00l textureas the predominant texture, a primarily recrystallized and normal graingrowth microstructure. The magnetic characteristic exhibited by thealloy approached those of commercially produced 3.25% silicon steels inuse today.

DESCRIPTION OF THE PREFERRED EMBODIMENT The alloy of the presentinvention has a composition which includes up to about 0.03% carbon, upto about 1% manganese, at least 0.3% up to about 4% of at least one ofthe volume resistivity improving elements selected from the groupconsisting of up to 2% silicon, up to about 2% chromium, and up to about3% cobalt, and the balance being essentially iron with incidentalimpurities. The carbon in the final product which is maintained as lowas possible is usually included with the composition initially fordeoxidation purposes in the normal melting of the components. While itis desirable to maintain the carbon content in the melt as low aspossible, up to about 0.03% can be employed without adversely affectingthe magnetic characteristics of the alloy as melted. With about 0.03%carbon, it is possible to decarburize the finished alloy and remove thecarbon content to the desired low level.

The alloy also contemplates the use of manganese in amounts up to 1%usually for the purpose of deoxidizing the material. It will be notedhereinafter however that the addition of manganese also improves thevolume resistivity of the alloy but not to the same extent as silicon.Good results have been obtained where the manganese content of the alloyis about 0.5%.

In order to improve the volume resistivity of the alloy, at least 0.3%and up to 4% of at least one element of the group consisting of silicon,chromium and cobalt is necessary in the alloy of the present invention.Where silicon is employed, amounts of up to 2% can be utilized in orderto improve the volume resistivity. Good results have been obtained wherethe silicon content is maintained within the range between about 0.5% to1.5%. The silicon content is preferably limited to the foregoing rangein order that the alloy will exhibit an open gamma loop to enable one toutilize a primary recrystallization technique for developing the desiredgrain texture within the alloy. Where chromium is used as the volumeresistivity improving element, a minimum of about 0.3% chromium shouldbe employed and amounts in excess of about 2% chromium should beavoided. Since cobalt also improves the saturation value of the alloy,up to about 3% is contemplated within the composition for improving thevolume resistivity as well as the saturation value of the alloy.Combinations of any two or all three of these resistivity improvingcomponents are particularly effective. Sulfur should be as low aspracticable since the element will not be removed during subsequentprocessing.

In this respect sulfur should not exceed about 0.012% and preferably itshould be below about 0.010%. It has been noted that sulfur appears toadversely affect the coercive force and hence the core loss propertiesof the alloys. In contrast to presently available commercial orientedsilicon-iron wherein sulfur unites with manganese to form a particlewhich is effective in developing a high degree of texture in the finalproduct, such mechanism is not believed to be involved in developing thetexture observed in the alloy of the present inven tion. Moreover, whenit is considered that in the commercially available material the finalheat treatment temperature is in excess of about 1000C which iseffective for dissacating the manganese sulfide, the sulfur is removedfrom the alloy after it has served its purpose. However, this can onlyoccur at temperatures in excess of about 1000C. In contrast thereto,once the open gamma loop alloy of the present invention is finished hotworking, it is never heated above its Ac, temperature. Consequently, anysulfur which is present will not be significantly reduced during suchsubsequent operations. Accordingly, it is necessary to control thesulfur content and outstanding results have been obtained where thesulfur content is maintained at about 0.005 maximum. The balanceconsists essentially of iron with the usual incidental impurities thatare found in the manufacture of magnetic alloys on a commercial scale.

The alloy having the composition as set forth hereinbefore is melted andis cast into ingots in the regular commercial manner. The metal may becontinuously cast into slabs or bars. The cast ingots are thereafter hotworked usually at a temperature within the range about 1000C and 1100Cto a desired intermediate gauge. Where the alloy is to be processed byemploying two-stage cold working operation it is preferred to hot workthe metal to a thickness of about 0.10 0.025 inch. On the other handwhere the alloy is to be processed by employing a three-stage coldworking opera tion, the preferred finished hot work gauge is about 0.180$0.030 inch. While it is not absolutely essential to protect the steelduring such hot working operation, an argon or other non-oxidizingatmosphere may be used in order to prevent excessive scaling of thealloy during such hot working. It is preferred to hot work the alloy ata temperature of about 1050C to the desired final hot work gaugedepending upon the cold working operation to which the alloy will besubjected. Following such hot working to the desired gauge, the alloy isdescaled, usually by pickling in order to remove any scale which mayhave formed on the surface thereof during such hot working operation.

Following hot working the alloy is thereafter cold worked in two or moreoperations or stages to finish gauge. Where cold rolling is employed itmay be usually necessary to pass the alloy strands a number of timesthrough said cold working rolls in order to attain the desired reductionin area. Regardless of the number of passes employed the several coldworking operations require an intervening intermediate anneal at atemperature within the range between about 750C and the Ac temperatureof the alloy being processed. Thus in a two-stage cold working of thealloy to finish gauge, the initial hot worked material of about 0.10inch in thickness is first cold worked-to about 0.025 inch and thenannealed for l hour at a temperature of about 850C in an atmospherepreferably of hydrogen having a dew point of less than about 40C.Thereafter the alloy sheet or strip is given the second stage coldworking to the finish gauge usually within a thickness of between about0.010 inch and about 0.014 inch.

Thus, in a typical exemplary two-stage cold working operation anapproximately reduction in crosssectional area is effected on the alloyin the initial cold working operation and, following intermediateannealing, a reduction in cross-sectional area of about 50% to finishgauge is produced in the second stage operation. Thefirst stage of coldrolling may effect high reductions of up to or more. It is imperativethat only moderate amounts of cold work be employed in the final coldworking operation such that the reduction in cross-sectional area willrange between about 50% and 75% reduction in cross-sectional area fromthe thickness or the cross-sectional area of the material ofintermediate gauge resulting from the initial cold working operation.Excellent results have been achieved where the final cold reductioneffects a reduction in crosssectional area of between about 60% andabout 70% to finish gauge.

Where thinner final gauge material is desired, advantageously athree-stage cold working operation may be performed with each coldworking stage being followed by an intervening intermediate anneal at atemperature within the range between about 750C and about the Actemperature of the alloy. In this three stage process, in each of thecold working operations only moderate amounts of cold work are effected,usually within the range between about 50% and about 75% reduction incross sectional area from the preceding gauge material.

Thus, a typical three-stage cold working operation would start with ahot work gauge of about 0.18 inch strand thickness, which strand isthereafter descaled, usually by pickling and annealing for about 5 hoursat a temperature of between 850C and 900C. The annealedalloy strand isthen first cold worked to a thickness of about 0.080 inch in thickness,i.e., 55% reduction, annealed for about 5 hours at a temperature withinthe range between about 800 and 900C, cold worked to a thickness ofabout 0.020 inch in thickness, (i.e. a 75% reduction) annealed for about1 hour at a temperature within the range between about 800C and 900C andthereafter cold worked to a finish thickness usually within the rangebetween about 0.005 and about 0.007 inch in thickness, a reduction ofabout 75% to 65%.

In both the two-stage and the three-stage cold working process, part ofthe cold working operation except the last one may be performed at anelevated temperature between room temperature and about 300C. Theworking at elevated temperatures is referred to as hotcold working. Suchhot-cold working can take place at any temperature above ,roomtemperature and below the recrystallization temperature of the alloybeing processed. Where such hot-cold working is employed in any of thecold working operations except the last, it is preferred to employ anargon atmosphere in order to reduce any tendency towards appreciableoxidation of the surface of the alloy strand being processed. Moreover,at each of the intermediate annealing heat treatments which areinterposed between the cold working operations, a protective atmosphereand preferably a hydrogen atmosphere having a dew point of less thanabout 40C is employed.

Moreover, it will be appreciated that one or more of the intermediateanneals can be accomplished by means of a strip anneal versus a boxanneal. Thus a single strand from a coil of the alloy may be continuousfed into a strip annealing furnace where the material is heated to atemperature typically of about 900C wherein each increment of the stripis maintained at this temperature for a time period of typically 3minutes. A hydrogen atmosphere having a dew point of 40C may beadvantageously employed.

Following cold working to finish gauge the alloy sheet or strip issubjected to a final anneal, usually a box anneal, at a temperaturewithin the range between about 750C and the Ac temperature of the alloysuch box annealing usually being carried out in an atmosphere ofhydrogen having a dew point of less than about 40C. The alloy ismaintained at a temperature which is always below the alpha to gammatransformation temperature in order to obtain a primary recrystallizedmicrostructure with normal grain growth. It has been found that thealloy so processed and subjected to the final annealing attains thedesired degree of orientation usually within a time period within therange between the 24 hours and 48 hours while at the box annealingtemperature. Upon cooling to room temperature following such boxannealing, the alloy will possess a grain structure having apreponderance of the grains aligned in the cube-on-edge or l l0)[00lorientation. It has been found that the grains which attain thepreferred orientation have cube edges which are aligned within tendegrees of the rolling direction.

In order to more clearly demonstrate the alloys and the processes of thepresent invention, below are examples of a number of heats melted andprocessed in ac- V cordance with the teachings of the present inventionand such alloy products demonstrate the desired (ll0)[00l] texture witha primary recrystallized and normal grain growth microstructure.Reference is directed to Table l which illustrates the chemicalcomposition of a number of alloys which were made and tested incomparison with a commercially available 3.25% silicon containing alloywhich was processed to produce a cube-on-edge orientation by a secondaryrecrystallization and preferred grain growth.

TABLE 1 HEAT %Mn 4C1 718i 'zc* olo-cm) .Excess for deoxidation Table 1also limits lists the resistivity (p) which was measured for the variousalloys. These alloys were made and processed in accordance with thefollowing outlined procedures.

PROCESS NUMBER 1 PROCESS NUMBER 2 I-Iot roll at l050C in argon to 0.180inch in thickness pickle and anneal 5 hours at a temperature within therange between 850C and 900C employing dry hydrogen. Warm roll at 260C,employing argon, to 0.080

-' inch. Anneal 5 hours at the intermediate annealing temperature ofabout 850C in dry hydrogen. Warm roll at 260C, employing argon to 0.040inch in thickness and thereafter cold roll to 0.020 inch in thickness.Anneal 1 hour at the intermediate annealing temperature between 850C and900C employing dry hydrogen. Cold roll to 0.007 to 0.005 inch inthickness.

Epstein strips were cut in the rolling direction and one inch diametertorque discs were punched from alloys which were finally annealed at atemperature of 850C to 950C for 48 hours in dry hydrogen and thereafterthe test specimens were furnace cooled. Refer- TABLE 3 Nominal ThicknessP615 P015 m al! un all! HEAT (mils) (W/lb (VA/lb) (W/lb) (VA/lb) (W/lb)(VA/1b) ence is directed to Table 2 which lists the torque and the DCmagnetic data.

The AC data definitely indicate that the highly textured alloys hadproperties approaching that of type M-S TABLE 2 Nominal Peak ThicknessTorque Peak H 13 B HEAT PROCESS (mils) (erg/cm) Ratio (k0) (1(0) Typicalcommercial values From the data set forth in Table 11, it may be seenthat the alloys which were processed using the Process 1 show that arelatively good (1 )[0O1] orientation was obtained in the alloyscontaining chromium and silicon. This is evident by the peak ratioswhich lie within the range between 0.42 and 0.50. Commercial 3.2%silicon steel with a peak ratio 0.34 has an excellent degree of 1 10){001 orientation. However, the peak ratios measured for heats 1482, 1483and 1484 establishes that a preponderance of the grains have the (110)[00l] texture developed therein. Note that while the B values arelower the saturation values B either are comparable or exceed the typeM-5 values. The coercive force is also quite good. An examination of themicrostructures of samples 1481, 1482, 1483 and 1484 indicated that allhad a primary recrystallized microstructure characterized by normalgrain growth.

Process 2 produced some general improvements in the peak torque valuesand slightly higher peak ratios in comparison with the commercial 3.20%silicon steel.

. mary recrystallization and normal grain growth. These However, onceagain the preponderating texture which was developed was thatcharacterized as (1 10)[00l In particular heat 1482 with 0.6% chromiumhas a B value identical to the commercially produced 3%% silicon steeland a B value higher than that of the commercial material. ,The siliconcontaining alloys namely useful textures have been obtained with alloyscontaining small amounts of chromium and silicon. Since both requireonly moderate final cold reductions with the final cold reductionplaying a major role in the texture development, a highly useful andinexpensive magnetic composition has been developed. The resultingalloys have B values equivalent to type M 5 commercial silicon steel andB values higher than commercially available silicon steel. The 60-1-12AC properties of the 6 mil material approach those values found for thecommercially available silicon steel.

In order to more clearly demonstrate the present invention, twocommercial size heats were made each having a composition within thelimits set forth hereinbefore. For comparative purposes, parallel datawere also obtained from Heat No. 1482 which was processed in accordancewith Process Number 2 set forth hereinbefore. The chemical analysis andthe electrical resistivity are set forth hereinafter in Table IV.

TABLE 4 Chemical Analyses and Electrical Resistivity %C HEAT lngot-After NO. "/(Si /zCr %Mn %S "k /LN Added Ladle Final Box (uQ-cm) Anneal'Nominal I All analyses were done on the ingot (or air melt ladle)samples except when indicated otherwise. I

Heats 3524 and 3523 were both air induction melted heats having a weightof approximately 5000 lbs. for

each heat. The 5000 lb. heat was cast into an ingot which was thereaftervacuum arc remelted, forged and separated into two billets for hotworking. One of the billets was hot rolled in air to 0.160 inches andthereafter part of the hot band material was processed as follows.

For heat 3524 the hot rolled band had a thickness of 0.160 inch. The hotrolled band was thereafter descaled, cold rolled to 0.08 inch, annealedfor 1 hour at 850C in dry hydrogen followed by cold rolling to 0.02 inchin thickness. The 0.02 inch thick material was then subjected to a stripanneal at 900C in an atmosphere of dry hydrogen. The material wasmaintained at the temperature of 900C for a time period of 3 minutes. 3After annealing, the material was cold rolled to a thickness of 0.006inch which was the desired finished gauge. Thereafter the finished gaugematerial was subjected to a final annealing for a time period of 48hours at a temperature of 900C while employing a hydrogen 3 atmospherehaving a due point of less than -C. The samples were placed in thefurnace cold and program heated at the rate of 50C per hour to 900C andafter holding at 900C for 48 hours, they were program cooled at 50C perhour until a temperature of 300C 40 was attained. From the foregoing, itwill be apparent that the processing of Heat No. 3524 involved athreestep cold rolling sequence and closely approaches Process No. 2 asset forth hereinbefore.

In contrast thereto, one of the billets from Heat No.

3523 was also hot rolled in air to the same hot rolled band thickness of0.160 inch. It was thereafter cleared by descaling followed by an annealfor 1 hour at a temperature of 850C in dry hydrogen. The first coldrolling involved a hot-cold rolling at a temperature of ing which thematerial was cold rolled to fi nish gauge of 0.006 inch in thickness.The finished gauge material was subjected to a final box anneal for atime period of 48 hours at a temperature of 850C while employing ahydrogen atmosphere having a dew point of less than 40C. In contrast, tothe processing for Heat No. 3524, the samples of Heat No. 3523 wereplaced into the furnace at temperature and following the annealing theywere program cooled at a rate of centigrade degree per hour until atemperature of 300C was achieved.

Reference is now directed to Table V which lists the DC magneticproperties as well as the torque data on the material as processed asset forth hereinbefore.

' TABLE 5 Torque Values and DC Magnetic Properties From an examinationof the Peak Torque data as well as the Peak Ratio it will appear thatthese data indicate a high degree of (l 10)[001 type orientation. Whilea perfect single crystal of 3% silicon-iron having a (ll0)[00l]orientation will exhibit a Peak Ratio of about 0.35 and a Peak Torque ofabout 215,000 ergs per cubic centimeter, these data indicate that a highpreponderance of the grains exhibit the (ll0)[00l] type orientation.

One interesting feature of the DC magnetic data indicate that thesaturation value nominally the B 'value, is approximately 21,300kilogauss. Comparing the B data with the saturation data, it is seenthat these alloys are so highly textured that they all exhibited inexcess of 85% of the saturation value at a magnetizing force of 10oersted, thereby confirming the high degree of texture within thealloys.

Reference is now directed to Table V1 which summarizes the AC magneticcharacteristics of the same heats as Table 4.

TABLE V1 Hz AC Magnetic Properties 2 HEAT Gage Pmmu P, (VA/lb) NO.(mils) l5 kG 17kG l8kG l9kG 20kG lSkG l7kG 18kG l9kG 20kG From Table VIit is seen that both the watt loss and aption of the {001 directionfrotn the rolling direction in parent watt loss of these materials isoutstanding when Table VI and these results tend to confirm the B valitis considered that the resistivity exhibited by the alues listedhereinbefore in Table IV. loys is less than one-half of the resistivityexhibited by In order to complete the analysis from the X-ray polecommercially available type M5 silicon steel. In this re- 5 figures, thehistogram results are set forth hereinafter spect Heat No. 3524 whichhad the lowest coercive i T bl VIIL force and the highest resistivityexhibited the best magnetic characteristics both from the core loss aswell as TABLE the apparent core loss standpoint.

In order to substantiate the grain texture or orienta- Histogram Resultstion developed in these alloys, both (110) and (200) a :10 Within 10 Z(100) Within 10 X-ray reflection pole figures and their correspondingSample of Shes! Surface of Sheet Surface histograms were taken on eachsample and are graphi- 60 6 l8 6 cally depicted in FIGS. 1 through 6 and1A through 6A, 352 67:3 :2 inclusive. An examination of the various polefigures 5 35230 tend to confirm the torque data, the magnetic proper mHismgmms H65 1 and ties and the domain analysts as IS set forthhereinafter. st-t- Histograms FIGS. 3 and 4.

As graphically illustrated in FIGS. 1 through 6, each If? fzfl f izi T;

t U" C C UT mu 1 IL"! contour shows multiples of iron random intensity,the L p digit and contour relationship being set forth in each 20Figure. The histogram data from the pole figures set forth in In orderto further verify the strong texture d v l- Table VIII and compared withthe data set forth by the oped in these alloys, a quantitative domainanalysis was domain n ly i in b e O S reasonably gOOd performed on eachof the samples to determine the volilgreemcht between the tWO. Thus, inmp i n With ume percent of the (l 10) plane within l2 of the samthetorque data especially the Peak Ratio, the presence ple surface.Commensurate with this same analysis, the 0f the Within 0f the ShCCt flfl g h r volume percent of the 100) plane which was found to With thealignment Ofthc Cube edges with the l or be within 12 of the samplesurface was l d t rolling direction would account for the higher valuesof mined together with the percentage f th grains i the peak ratio aswell as the peak torque set forth herewhich the [001] direction waswithin various angles in inbefore for Table IV.

degrees of the rolling direction. These results are set From the g g, itis Clear that alloys having the forth hereinafter in Table VII.composition set forth within the limits enunciated here- TAELE VII IQuantative Domain Analyses HEAT Vol. of I I0) Vol. of I00) of Grainswith of Grains with Average Deviation of NO. within 12 of within 12' of[001] within 10 [00]] within l5 [001] from Sheet Surface Sheet Surfaceof RD of RD" RD" 'RD Rolling Direction From the test results set forthin Table Vll, it is seen inb f r n processed in rdance with the mannerthat each of the samples have in exccss of of the e f r h her in f r prstanding magnetic volume of the grains having the 1 l0) plane within 12characteristics which are developed in these alloys of the sheetsurface. It is interesting to note that there through a major portion ofthe grains having been oriis a component of the (100) plane within 12 ofthe 50 ented into the cube-on-edge 0r( l0)l001]0Ylehtati0nsheet surfaceand in each instance this volume turns out This texture is achieved inwhich the final product is to be between 15 and 25%. Since both the (l10) and characterized by a primarily recrystallized and normal the (100)textures are present and the cube edges are grain growth structure whichcontributes significantly strongly aligned in the [001] direction, thesedata tend to the observed magnetic characteristics as set forth toconfirm the magnetic data especially the torque hereinbefore.

analysis set forth hereinbefore. In contrast to the production ofcommercial 3% sili- These quantitative domain analysis were performedcon steel, the alloy of the present invention does not reon threeEpstein samples which were scanned over a quire a separatedecarburization anneal prior to the distance of 0.5 centimeters. Thealignment of the easy final box anneal. It has been found that employingeidirection of magnetization, that is, the [001] with the ther ProcessNo. l, or Process No. 2, neither of which rolling direction of thesamples was determined by employs a wet hydrogen decarburization anneal,the measuring 50 grains either the (110) or the (100) in alloy oftenfinal box annealing will exhibit a carbon the samples using a specialoptical goniometer attachcontent of nominally less than about 0.003%.Actual ment to a metallograph. In all cases, the volume percarbonanalysis from both the ingot condition and after cent of the sample withthe (1 l0) planes within 12 of final box anneal are set forthhereinbefore in Table IV. the sheet surface far exceeds 50%. Moreover,with the Where desired, however, a decarburizing anneal may minor (I00)planar component being aligned in the be employed in order to obtainextremely low carbon same manner as the I I0) plane the improvedmagcontents without adversely affecting the magnetic charneticcharacteristics are noted. Thus, there is also reaacteristic exhibitedby the alloy.

sonable agreement between the average angular devia- Comparable resultswill be obtained by adding cobalt to about 4% of a volume resistivityimproving elementselected from the group consisting essentially of, upto 2%silicon, up to 2% chromium, and up to 3% cobalt, and the balanceessentially iron with incidental impurities, the alloy having a majorporportion of the grains exhibiting a 1 texture and in which a majorproportion of the oriented grains have cube edges of their crystallattices aligned within 12 of the rolling direction, and primaryrecrystallized and normal grain growth microstructure.

mium content is within the range between about 0.3 to about 0.9%.

3. The alloy member of claim 1 in which the silicon content is withinthe range between about 0.5% and 1.5%.

4. A heat treated alloy member having an open gamma loop and improvedmagnetic characteristics consisting essentially of up to 0.03% carbon,up to 0.5% manganese, less than 0.010% sulfur, from 0.3% to 4% of atleast one of the volume resistivity improving elements selected from thegroup consisting essentially of up to 2% silicon, up to 2% chromium, andup to 3% cobalt, the balance being iron with incidental impuri-' ties,the alloy having a major proportion of the grains exhibiting a 1 10)texture and in which a major proportion of the oriented grains have thecube edges of their crystal lattices aligned within 12 of the rollingdirection, and a primary recrystallized and normal grain 2. The alloymember of claim 1 in which the chrogrowth microstructure.

1. A HEAT TREATED ALLOY MEMBER HAVING AN OPEN GAMMA LOOP AND IMPROVEDMAGNETIC CHARACTERISTIC CONSISTING ESSENTIALLY OF UP TO 0.03% CARBON, UPTO 1% MANGANESE, LESS THAN 0.012% SULFUR, FROM ABOUT 0.3% TO ABOUT 4% OFA VOLUME RESITIVITY IMPROVING ELEMENT SELECTED FROM THE GROUP CONSISTINGESSENTIALLY OF, UP TO 2% SILICON, UP TO 2% CHROMIUM, AND UP TO 3%COBALT, AND THE BALANCE ESSENTIALLY IRON WITH INCIDENTAL IMPURITIES, THEALLOY HAVING A MAJOR PORPORTION OF THE GRAINS EXHIBITING A (1109 TEXTUREAND IN WHICH A MAJOR PROPORTION OF THE ORIENTED GRAINS HAVE A CUBE EDGESOF THEIR CRYSTAL LATTICES ALIGNED WITHIN 12* OF THE ROLLING DIRECTION,AND PRIMARY RECRYSTALLIZED AND NORMAL GRAIN GROWTH MICROSTRUCTURE. 2.The alloy member of claim 1 in which the chromium content is within therange between about 0.3 to about 0.9%.
 3. The alloy member of claim 1 inwhich the silicon content is within the range between about 0.5% and1.5%.
 4. A heat treated alloy member having an open gamma loop andimproved magnetic characteristics consisting essentially of up to 0.03%carbon, up to 0.5% manganese, less than 0.010% sulfur, from 0.3% to 4%of at least one of the volume resistivity improving elements selectedfrom the group consisting essentially of up to 2% silicon, up to 2%chromium, and up to 3% cobalt, the balance being iron with incidentalimpurities, the alloy having a major proportion of the grains exhibitinga (110) texture and in which a major proportion of the oriented grainshave the cube edges of their crystal lattices aligned within 12* of therolling direction, and a primary recrystallized and normal grain growthmicrostructure.